1. Field of the Invention
The present invention relates to a light emitting device using a light emitting element and a method of manufacturing the light emitting device, particularly to a light emitting device in which a light emitting element is sealed with a resin, and to a method of manufacturing the light emitting device.
2. Description of Related Art
A light emitting device using a light emitting element is small in size and has a low power consumption with long service life, and is used in a wide variety of applications such as backlight for liquid crystal displays and in-car devices. Typically, the light emitting element is sealed with a resin when it is incorporated in a light emitting device for protection of a wire-bonded portion and other wiring portions, and for protection of the light emitting element itself.
Light emitted from the light emitting element is a single-color light such as red, green, or blue, and a fluorescent material for converting it to light having a different wavelength may be used in combination with the light emitting element. For example, a light emitting device is known, which is capable of emitting white light by additive mixing of colors of the light emitted from an LED exiting directly to the outside and the wavelength-converted light emitted from the light emitting element.
Conventionally, a light emitting device having a light emitting element sealed with a resin which contains a fluorescent material is disclosed for example in JP 2005-277331A, in which the density of the fluorescent material in the resin and the viscosity of the uncured resin are adjusted to minimize deposition of the fluorescent material and to prevent the fluorescent material from covering the surface of the light emitting element.
With this, a decrease in the light extraction efficiency of the light emitting element and loss in propagation of light caused by the fluorescent material are suppressed and thus improvement in the emission intensity of the light emitting device are obtained.
Also, a semiconductor light emitting device having a light emitting element sealed in a resin package is disclosed for example in JP 2000-164937A in which the resin package has a two-layer structure of a sealing resin layer and a fluorescent material layer containing a fluorescent material for converting the emission wavelength, where the two layers include a resin as a common material, and the fluorescent material for converting color of light is arranged in the vicinity of the light emitting element.
This arrangement suppresses occurrence of detachment at the interface between the resin layers and an optical warpage due to encapsulation with a plurality of resin layers, and to reduce exposure of the fluorescent substance near the surface of the resin layer to external light so that emission caused by an excitation of the fluorescent substance by external light can be prevented.
However, in such a light emitting device described in JP 2005-277331A, the fluorescent substance is dispersed in a resin, so that light from the light emitting element hits the fluorescent substance dispersed in the resin multiple times and attenuates. Also, a difference occurs in the amount of resin used to seal the light emitting element by way of potting or printing, resulting in difference in the amount of the fluorescent substance included in each of the light emitting devices. Accordingly, the difference in the amount of light increases between the light from the light emitting element and the wavelength-converted light from the fluorescent substance which absorbed the light from the light emitting element. In such a semiconductor light emitting device described in JP 2000-164937A, the fluorescent substance is over-packed in the vicinity of the light emitting layer of the light emitting element, which makes it difficult to extract light from the light emitting element to outside and may result in color unevenness.